A gas turbine blade has a tip that closely brushes a surrounding shroud. The shroud channels the working gas flow through circular arrays of blades. Each circular array is called a turbine stage, the first stage being just after the combustion section. The inner lining of the shroud is made abradable so that the blade tips can cut a path in it to minimize the blade tip-to-shroud clearance. This minimizes leakage of the working gas from the pressure side to the suction side of each blade. Some blade designs include a tip shroud as shown in FIG. 1, which is a plate on the blade tip. A seal rail may extend radially outward from the plate. The rail is aligned circumferentially along the rotation direction. It cuts a narrow groove in the shroud lining for working gas sealing. The rail may include wider portions called teeth that cut the groove wider than the rail to allow for proper blade to shroud clearances for tolerances and rotor axial movement.
A disadvantage of adding a tip shroud and seal rail to a blade design is added weight. Cantilevered portions of the tip shroud must be rigid to resist flexing from centrifugal force. This limits possible weight reductions.